roughage

Any rough or coarse material.

Rough or coarse material; something for rough use, as straw for bedding animals.

In stock-feeding, the coarser portion of a ration, as hay, corn silage, etc., containing relatively little nutritive matter, as opposed to the concentrated part or grain feed.

dietary fibre

coarse, indigestible plant food low in nutrients; its bulk stimulates intestinal peristalsis